The invention relates to a modular high-frequency converter. The invention further relates to a method for operating such a converter.
A converter circuit of the aforementioned type is disclosed in the publication by Lukas Lambertz et al., “Modularer Hochfrequenz Umrichter für Fahrzeugantriebe (Modular High-Frequency Converter for Vehicle Drives)”, EMA 2010, 8-9, Sep. 2010, Aschaffenburg for supply of electric energy to the motor windings of an electric drive motor in a vehicle drive.
The known modular high-frequency converter (abbreviated to MHF converter) is designed to convert a DC voltage from a traction battery of the vehicle into a number of AC voltages. The individual AC voltages are created in such cases by a number of submodules, which are connected in series into the power supply circuit of the traction battery. In this converter each submodule is linked on its input side via a single-phase half bridge to the power supply circuit. To create the AC voltage each submodule has on its output side a single-phase full bridge (H bridge), which is connected via a load circuit to a phase winding of the drive motor of the vehicle. Within the submodules the input-side half bridges and the full bridge are connected in parallel together with an intermediate voltage capacitance in a (DC voltage) intermediate circuit.
In normal operation (drive mode) of the MHF converter, in which electrical power is transported from the power supply circuit via the submodules of the converter into the respective load circuit, the input half bridges are operated in conjunction with an inductance disposed in the circuit as a boost converter.
For this purpose the submodules are usually connected to the power supply circuit in a regularly alternating sequence. The input-side half bridges are usually activated for this purpose with periodic carrier signals, which are offset by the same phase angle. As a consequence of this activation the intermediate circuit capacitance of the respective connected submodule is connected into the power supply circuit for the duration of a connection pulse.
In addition to the drive mode, the input-side half bridges of the submodules can be operated in an energy recovery mode, in which the electrical power from the load circuit is fed back via the respective associated submodule into the power supply circuit. The input-side half bridges of the submodules are operated for this purpose as buck converters.
The intermediate circuit voltages of the submodules are regulated for each submodule individually by variation of the duration of the respective connection pulse.